Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: Using IF statements with maths where the input is not an integer
Top Forums Shell Programming and Scripting Using IF statements with maths where the input is not an integer Post 302546812 by StudentFitz on Friday 12th of August 2011 08:29:21 AM
Old 08-12-2011
Using IF statements with maths where the input is not an integer
Hi All

I've made a few scripts which using GDAL extract the value of a pixel within a given raster. The purpose is to work out the combine value of every pixel. I thought there may have been an easier way to do this but alas!

The code below extracts the pixel value at position X Y. The value is a floating point rather than an integer and thats where my problem lies. The if statement simply exports the value to a txt file. Other scripts take care of the rest ie change values of X Y and summing the resultant txt files.
Code:
#!/bin/sh
input=`gdallocationinfo -valonly 210_1515_volume.env X Y`  # The value of the pixel at coordinate X Y
if [ $input -gt 0 ] ;then
	echo $input > colrow.txt
fi

However, I get the following message back when ever my statement is true because my value isn't an integer;

extract2.sh: line 4: [: 2.15787172317505: integer expression expected

Please note the raster file mostly contains zero values, and its only the values greater than zero I'm interested in, which is why I added the expression.

Any ideas how I can alter this code so the IF statement excepts integers? Alternatively if anyone knows of a faster method of quickly summing the values of a raster file, that would be equally useful.

Many thanks in advance for any assistance you can offer.

Andy
Last edited by vbe; 08-12-2011 at 09:50 AM.. Reason: please use code tags!
 

10 More Discussions You Might Find Interesting

1. Shell Programming and Scripting

Problem with Maths

Heres a script i wrote as a bit of practise. What it does is insert a line in the middle of a file. The line being $1 and the file being $2 #!/bin/bash rm tempfile touch tempfile count=1 linenum= `wc -l < $2` if then echo $1 >> $2 else even=`expr "$linenum" % 2` if then... (3 Replies)
Discussion started by: Quesa
3 Replies

2. Shell Programming and Scripting

isql input file with multiple sql statements

I've got: isql -U $USERID -S $SERVER -D $DATABASE -i inputfile.sql -o outputfile.txt in inputfile I have: go sql#1 go sql#2 go sql#3 go I also tried without "go" and with";" instead which did not work SQL statements will work if I paste them directly into the script and use EOF ... (0 Replies)
Discussion started by: Cailet
0 Replies

3. Shell Programming and Scripting

Perl - maths equation - need help

if input to the perl program is ' ( p * ((a+b) * (c+d))) + q ' it shuld give the output as ' pac + pad + pbc + pbd + q ' .can anyone suggest a way to do this ? (7 Replies)
Discussion started by: Anuj8584
7 Replies

4. Programming

How i can read a long integer from standar input and a string with as many characters as specified..

how i can read a long integer from standar input and a string with as many characters as specified in the number? i thing that i must use the read command ofcourse.... (6 Replies)
Discussion started by: aintour
6 Replies

5. Shell Programming and Scripting

Maths with variables

Hello, I'm trying to write a while loop for a decimal value in tcsh which I know can't be done. Instead I want my increments to be one order of magnitude too large and then divide it by 10 when I use the variable. However, I don't know how to divide my variable and set it as another. set... (1 Reply)
Discussion started by: DFr0st
1 Replies

6. UNIX for Dummies Questions & Answers

Check if input is an integer or a floating point?

Hiii I actually intent to check the integer or floating point number input by user i.e. 23, 100, 55.25, 12.50 ..etc. However, when someone input strings or alpha character, my program has to show invalid input.!! Is there any Unix shell script syntax can help me to check ? Thanking you (2 Replies)
Discussion started by: krishnampkkm
2 Replies

7. Programming

I don't know how to replace input char with appropriate integer

Hi guys, I asked for help on programming forums and no one didn't helped me so I ask for help here. I am playing with some tasks from my book and I can't figure where did I get wrong. From the first program I get a blank screen, program won't generate 10*10 matrix. And second problem is I... (6 Replies)
Discussion started by: solaris_user
6 Replies

8. Shell Programming and Scripting

Simple maths calculator loop.

Hi, I am trying to make a maths calculator that: 1. Prompts the user for a number. 2. Prompts the user for an operation (add, subtract, divide or multiply) 3. Prompts the user for a number. 4. Prompts the user for another operation (same as above) OR the option to get the result for the... (4 Replies)
Discussion started by: johnthebaptist
4 Replies

9. Shell Programming and Scripting

Maths in shell scripts

Hi, Need help on this. I need to increment a variable by 1 but retain as 2 characters. I am using expr to do additions: NEWSERIAL=`expr $SERIAL + 1` $SERIAL can range from 01-99. After adding "1", I need the result to be 2 characters, eg: 02+1 = 03. By default expr will truncate the... (4 Replies)
Discussion started by: vchee
4 Replies

10. Shell Programming and Scripting

Calculate the constant e to 14+ decimal places using integer maths.

Hi guys... I am loving this integer maths thing. 64 bit systems are certainly easier than 32 bit, but hey, I don't intend to leave out my fav' platform. Using one of the 'Brothers' methods, URL inside the code. #!/bin/sh # # #!/usr/local/bin/dash # e_constant.sh # Brother's formula . #... (2 Replies)
Discussion started by: wisecracker
2 Replies

LEARN ABOUT DEBIAN

vinvert

vinvert(1Vi)															      vinvert(1Vi)

NAME

       vinvert - invert image pixel values

SYNOPSIS

       vinvert [option ...] [infile] [outfile]

DESCRIPTION

       vinvert inverts each input image to produce a corresponding output image. The operation is suitable for swapping black and white in a grey-
       scale image.

       Each output pixel is computed from the corresponding input pixel by

	      out-pixel = M - in-pixel

       where M is the maximum value allowed by the pixel representation, or 1 in the case of float or double pixels. Input pixel values  must  lie
       in the range [0,M].

       Each output image has the same number of bands, rows and columns, and the same pixel representation, as the corresponding input image.

COMMAND LINE OPTIONS

       vinvert accepts the following options:

       -help	      Prints a message describing options.

       -in infile     Specifies a Vista data file containing the input images.

       -out outfile   Specifies where to write the output images as a Vista data file.

       Input and output files can be specified on the command line or allowed to default to the standard input and output streams.

SEE ALSO

       vnegate(1Vi), vop(1Vi), VImage(3Vi), Vista(7Vi)

AUTHOR

       Art Pope <pope@cs.ubc.ca>

Vista Version 1.12						   24 April 1993						      vinvert(1Vi)
All times are GMT -4. The time now is 05:55 PM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy